Playing against a more attacking side like Bayern Munich shouldn't be only defending, is all about attack attack attack. A 1nil lead is never going to decide who's going to be the winner not while you have about 45'mins more to play. No wonder better players don't stay long in the team instead they leave and it helps them win trophies they could not win with the team. Dortmund has never been a stronger team ever since they couldn't get that trophy off Bayern, if they couldn't get 3pt in this first leg I don't think a point can be gotten in the return leg because Bayern would want to maintain that spot that's if they'll still be at the top and we all know that Dortmund can never be relied on to stop Bayern Munich from winning the trophy this season.
I don't think you should be attacking always when playing against a team that you know is better than you and they love to score lots of goals. You should be defending and when the opportunity comes out then you counter attack to get your own goal and go back to defending. Playing against Bayern Munich and attacking them without focusing on defense, you'll concede alot of goals and then lose the match in a large margin but if you're defending and you still lose. It isn't going to be too much losses. The strategy should be simple when playing against Bayern Munich, wait for them to make a mistake and make them pay for it. Don't try to go toe to toe with them unless you're as strong as they're too.